Optics: measuring and testing – By polarized light examination – With light attenuation
Patent
1993-11-12
1995-04-18
Evans, F. L.
Optics: measuring and testing
By polarized light examination
With light attenuation
356385, 250560, G01B 1124
Patent
active
054083257
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
a. Field of the Invention
This invention relates to an apparatus for measuring the profile of a moving object. Once the profile of the object has been measured it may be compared against predetermined dimensions, for example to determine whether or not the object has been damaged. The invention is particularly, although not exclusively, used for determining the profile of coiled tubing used in the oil and gas industry, but may also be used for measuring the profile of extruded objects made by a continuous process, or objects in automated transfer lines, or hawser or cable during lifting.
b. Description of the Related Art
A known apparatus for measuring the profile of an object is disclosed in U.S. Pat. No. 4,800,104. It is known to check the internal profile of a tubular member by optically scanning the entire 360.degree. of the surface with a light beam and to receive reflected energy which may be transmitted to electrical energy to provide a trace on a C.R.T. which may then be compared with a predetermined trace. Such an apparatus is mechanically complex and has electronic components requiring electrical power at the measurement station. In an oil and gas well drilling situation a so-called zone 1 permits electrical power, whereas a so-called zone 0 must have no electrical activity to avoid explosions and such a zone 0 station is at the top of a well head.
The present invention seeks to provide an apparatus for measuring the profile of a moving object suitable for use in a zone 0 situation.
SUMMARY OF THE INVENTION
According to this invention there is provided an apparatus for measuring the profile of a moving object comprising at least two spaced light emitting means and light receiving means for receiving illumination therefrom, the light emitting means being positioned on one side of a passage through which said object is movable and the light receiving means being positioned on another portion of said passage so that a particular profile of the object may be measured and the positioning of the light emitting means and light receiving means being such that the object partially cuts the light received by the light receiving means, processing means connected to the light receiving means for measuring the profile of said object from one of the illuminated portions of the light receiving means and the non-illuminated portion thereof, characterized by said light emitting means including light projecting means disposed at least partially around said passage and positioned to emit light beams along different angularly directed paths, said light receiving means also being disposed at least partially around said passage, said light projecting means and said light receiving means being located in a cassette housing, said cassette housing having an aperture defining said passage, and means for pressurizing said housing.
Preferably said pressurizing means is a gas pressure means connected to said housing for increasing the internal pressure thereof above atmospheric pressure, and a gas pressure detector is provided for detecting said housing internal pressure and in dependence upon said housing internal pressure being adapted to cut off electrical power to said apparatus.
Preferably, each light emitting means is a light emitting diode or laser diode and said light receiving means is a linear array of elements having a pitch of less than 0.00254 mm. Conveniently, the processing means includes a comparator for comparing the measured profile with a predetermined set of profile values and for producing a signal representative of the difference therebetween.
Advantageously, the light output from the light emitting means is collimated by a lens, or a line optic lens provided to produce parallel light rays. Alternatively, the light emitting means include light source means and collimating means remotely positioned therefrom, a fibre optic cable linking said light source means and said collimating means so that only optical components are located in said housing, and an opto-electric elect
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Cruickshank Partners
Evans F. L.
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